Model Altitude For A Given Area...
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Hi folks,
I love the windy app, I use it and recommend it all the time, as a premium user of this product. I use it for my community weather website (20,000+ suscribers) in the Blue Mountains of Australia, 100km west of Sydney, at 1100M above sea level, where I live.
I have a question. When I click on the sounding option for my area, I get the model altitude of around 800M and the actual altitude of my town of around 1080M. This allows me to make adjustments for the model sounding altitude and my actual altitude. I live in an area of greatly variable terrain, where my village is at 1100M but just a few kilometres to the east or west, it might be only 500M in altitude.
My question:
When I look at the Windy Basic Forecast rendition from ECMWF model for my area, am I looking at the actual temperature forecast for my altitude of 1080M or are the temperature forecasts actually for the model altitude of around 800M, like they are in the sounding option?
Many thanks for such a fine application and thanks to everyone that works so hard, producing it! :)
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@temp850
Hi,
When you look at forecasts with different models, not only that of ECMWF, the predicted surface parameters are shown at model altitude. In your case at 800m but not at 1080m.
Weather models include just a coarse orography model. This is one of the reasons why in mountains global models are pretty wrong except if by chance you live at one of the model altitudes.
In mountains it is better to rely on high resolution models but Windy don’t offer this possibility, may be not yet, in Australia.To give an idea of the resolution effect of model:
https://community.windy.com/topic/8106/huge-differences-between-models?_=1634798809757This long thread underlines the temperature problem in mountains:
https://community.windy.com/topic/5297/surface-temperature-wind-doesnt-show-earth-s-surface-values?_=1634800226015We could imagine that Windy provide a corrected temperature line in Meteogram taking into account the real altitude of the location as explained by @Gkikas-LGPZ in this thread, with the Standard Atmosphere's lapse rate (6,5/1000m) correction.
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Thanks for taking the time to reply.
I do the snow and storm forecasting etc for my region via my website and I usually find Windy very good, when I use the atmospheric parameters at 900hPa, 850hPa, 700hPa and 500hPa etc.
When using the meteograms and airgrams, it is also very instructional and quite accurate. It is even possible to predict isothermal layers during marginal snow conditions, which is the norm in Australia. Our snow usually falls as wet snow, sometimes a lot of it.
I have looked today at four different town forecasts in the Blue Mountains of NSW at approximate altitudes of 1100M, 1000M and 900M and 800M and each of these towns via the basic forecast on Windy app showed different temperatures throughout the day by a degree or two. So, there must be some adjustments made in this regard.
I'm just not sure how and what is done.
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@temp850
This is probably due to the interpolation between grid points which are 9km spaced with the ECMWF model. And each of your locations are at a different distance from grid points. They don’t show the same interpolated temperature.
This old sketch may explain it:
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Thankyou.
This is my photo of the Blue Mountains region, where I live. The towns and villages in the Blue Mountains sit atop the eroded plateau and then the valleys are quite deep, within a few km of the towns. So yes, the lower resolution of the models averages out the altitude quite a lot.
I use the temperature at 900hPa and 850hPa during potential snowfalls, to determine the possibility of snow settling or indeed sleet or cold rain. As well as temperature etc, at 700hPa and 500hPa to determine possible convective snowfalls or maybe only isothermal snowfalls. I was successful on each occasion this year in forecasting our snow events and even was accurate with the amount of settling snow. Thanks to Windy app in part, this was made much easier.
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@temp850
Beautiful mountains, I remember seeing them in the background from the Sidney hinterland. -
Yes, there is a group of us that, for decades, have focused on the difficult task of forecasting snow for the Blue Mountains and Central Tablelands forecast district. Snow in Australia outside our ski fields is a real novelty and is usually very marginal. The challenge of forecasting it, is very enjoyable for a few dozen of us!
This is a shot from our snow this winter, August, 25th in this instance.
